Telephone system



Oct. 22, 1935. P. A. BOLANDER TELEPHONE SYSTEM Filed Feb. 25, 1952 Patented Oct. 22, 1935 PATENT OFFICE TELEPHONE SYSTEM Phillip A. Bolander, Chicago, Ill.,

assignor, by

mesne assignments, to Associated Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application February 25, 1932, Serial No. 595,133 13 Claims. (01. 179-227) This invention relates to telephone systems in general, and is concerned particularly with trunk circuits for use in such systems. The object of the invention is to increase the efiiciency of circuits of this type by arranging them so that they cannot be unnecessarily withheld from service when not actually in use.

The trunk circuit comprising the invention is particularly suitable for interconnecting an automatic exchange and a manual exchange or toll switchboard. It is desirable, of course, that trunks used for this service be freed immediately upon the termination of each call so that the trunks can be used eificiently. According to the usual practice, in handling this type of traflic, the manual operator is given disconnect supervision by the subscribers hanging up at the termination of a call. The operator is expected to may be unable to respond promptly to the disconnect signals, with the result that trunks are unnecessarily tied up at a time when they are most needed.

The unnecessary busying of trunks in the above manner has been overcome in the past by arranging the cord circuits so that the tip, ring, and sleeve conductors were opened automatically upon the termination of a call. An.

arrangement of this kind is shown in Gardner Patent No. 1,727,592, of September 10, 1929. Although arrangements ofthis kind have proven generally satisfactory, they are not entirely practical new automatic exchange to an old manual exwhen the two exchanges are under different ownership. Further, the modification of the cord circuits may not be economical when relatively few trunks are involved, as is the case in many systems. The present invention, on the other hand, contemplates the use of existing cord circuits without modification while still providing the automatic release feature. This is accomplished by associating the release apparatus with the trunks rather than with the cord circuits, and constitutes the main feature of the invention.

One embodiment of the invention is disclosed in the accompanying drawing, which represents a connection set up over a switch train in an automatic exchange to a trunk terminating in an operators position in a manual exchange. The subscribers line A, which may be of any well-known type commonly used in automatic telephone systems, terminates in the lineswitch LS. Lineswitch LS has access to selectors such as the selector S, and the selector in turn has access to local trunks and the trunks extending to the manual exchange. The trunk terminates in a simple trunk circuit change, which may be of the type disclosed in Wicks, Patent No. 1,583,240 of May 4, 1926. The equipment T, terminating the trunk at the manual exchange, is shown in detail and will be described hereinafter. trunk is provided with two jacks, J and J l which are located on the face of the switchboard, and],

if desired, may be multiplied in a plurality of positions.

When the subscriber at substation A extends a is call over the switch train to trunk circuit TC, battery is connected to the trunk conductor l, and, since trunk conductor 2 is normally connected to ground, relay 3, which is bridged across the distant end of the trunk line by way of. con- 20 tacts l3 and I4, energizes. Relay 3 completes a circuit by way of contacts l2 and 28 for lamp L. The lamp glows to notify the operator of the call awaiting attention. The operator answers the call by inserting the plug P of a cord circuit into 25 jack J, thereby closing a bridge across the two talking conductors of the trunk and completing a circuit over the sleeve conductors of the plug and jack for relay 8. Relay 8 is slightly slow to operate, and, before it actuates its armatures, 3o relay It! operates over the newly-completed loop circuit and completes a circuit for relay 6 at contacts 3|. Relay 6 operates, opens contacts [8 to prevent the operation of relay 9, and prepares a circuit at contacts l9 for relay 4. Relay 8 35 now operates, prepares a circuit for relay 9 at contacts 2 l, prepares a locking circuit for relay 9 at contacts 22, and completes the circuit for relay 4 at contacts 23. Relay 9 does not operate at this time due to the opening of contacts I8. 40 Relay t operates and disconnects relay 3 from the trunk at contacts l3 and Id. The operator may now converse with the calling subscriber; and extend the connection over the cord circuit in any well-known manner. 45

At the termination of the connection, it may be assumed that the calling subscriber restores his receiver in the usual manner, thereby causing the opening of the battery feed circuit at the trunk circuit TC. Relay It] accordingly deener- 50 gizes and opens the circuit of relay 6. Relay 6 restores, opens the circuit of relay 4 at contacts l9, and completes the tacts I8. Relay 9 operates and locks by way 01' contacts 26 and 22. The trunk is accordingly 55 T0 at the automatic ex- 5 It may be noted that the 10' disconnected from jack J by the opening of contacts 24 and 39, and connected to jack J I by way of contacts 25 and 29. The signalling circuit is also disconnected from lamp L at contacts 28 and connected to lamp L at contacts 21. Relay 9 is now locked up under control of relay 8, which, of course, will remain operated as long as the plug P remains in jack J. The supervisory relay of the cord circuit will, of course, restore and give the usual disconnect supervision responsive to the subscribers hanging up. As soon as the connection is pulled down, relay 8 restores and opens the circuit of relay 9, which likewise restores, and transfers the trunk back to its normal connection to jack J.

In case the operator should delay in pulling down the connection, a second call may come in over the trunk, in which case relay 3 will again operate, and at contacts l2 complete a circuit for lamp L. Lamp L glows to notify the operator of the incoming call, and the fact that this call comes in over the auxiliary jack indicates the failure to pull down the connection previously completed over the regular jack. The operator, however, may answer this call by inserting the plug PI of a cord circuit into jack J I, thereby completing a loop circuit for operating relay l0, and also a circuit over the sleeve conductors of the plug and jack for operating relay 5. Relay Ill operates quickly and completes the circuit for relay 6, which also operates, opens a point in the circuit of relay 1 at contacts 3| and prepares the circuit of relay 4 at contacts l9. Relay 5 is slightly slow to operate, and after an interval actuates its armatures, completes an additional holding circuit for relay 9 at contacts l6 and completes a circuit for relay 4 at contacts l1. Relay 4 operates as in the previous connection, and disconnects relay 3 from the trunk. The operator may now converse with the calling subscriber and complete the connection as required.

As previously stated, the arrival of the call over the auxiliary jack indicates the failure to pull down a connection established over the regular jack, and it is expected that the operator will take the necessary steps to have such connection taken down. As soon as the subscriber in the present connection hangs up, the trunk will, therefore, be transferred back to the regular jack so that the failure to pull down the connection over the auxiliary jack will not busy the trunk. The transfer in this case is efiected by the release of relays l0 and 6, the latter relay completing a circuit by way of contacts l5 and 3| for relay 1. Relay 1, by opening contacts 2!), permits relay 9 to restore and transfer the trunk from jack J I and lamp L to jack J and lamp L. A new call coming in at this time will, therefore, cause the lighting of lamp L, and the call will be answered over jack J in the usual manner.

What is claimed is:

1. In a telephone system, a trunk terminating in a jack, an auxiliary jack for the trunk, an operators cord circuit adapted to be connected to said first jack to answer a call extended over the trunk, and automatic means for transferring the trunk from the first jack to said auxiliary jack responsive to the calling party disconnecting from the trunk prior to the disconnection of the cord circuit from said first jack.

2. In a telephone system, a trunk, two jacks adapted to be connected to the trunk one at a time, cord circuits for connection with said jacks in answering calls extended over the trunk. and

means controlled by the trunk becoming idle while a connection to one jack exists for disconnecting the trunk from said one jack and for connecting it to the other jack.

3. In a telephone system, a trunk having talking conductors terminating in a jack, means for extending a call over the conductors of said trunk from a calling party to said jack, manual means for answering and further extending the call by connecting the conductors of said trunk 10 to said manual means by way of said jack and means controlled by the calling party upon hanging up his receiver for disconnecting the talking conductors of said trunk from said manual means.

4. In a telephone system, a trunk circuit hav- 15 ing talking conductors terminating in a jack,

a calling line and means for connecting it with the conductors of said trunk circuit, means including an operators link for connecting the conductors of said trunk circuit with a called line to 2 complete a talking connection by way of said jack, and means in the trunk circuit controlled over the calling line for disconnecting the talking conductors of the trunk circuit from said link.

5. In a telephone system, a trunk having two 25 branches at one end, means for extending a call over the trunk and one of said branches, means for answering the call, and means responsive to the calling party terminating the call for switching the trunk from said one branch to the other 30 branch.

6. In a telephone system, a trunk having two branches at one end, means for extending a call over the trunk and one of said branches, means for answering the call, and means responsive 35 to the calling party terminating the call for conditioning the trunk so that a succeeding call will be extended over the trunk and the other of said branches.

7. In a telephone system, a temporary con- 40 nection extending from a calling station over a trunk and one of two branches thereof to an operators link circuit, means controlled from said station for terminating the connection, and means responsive to the termination of the con- 45 nection for temporarily connecting the trunk to the other of said branches pending the disconnection of the link circuit from said one branch.

8. In a telephone system, a trunk having two branches at one end, means for extending a con- 50 nection to the other end of the trunk, means for connecting with one branch of the trunk to further extend said connection, means for terminating the connections to both the trunk and said branch, and means responsive to the termi- 55 nation of the connection to the other end of the trunk prior to the termination of the connection to said one branch for disconnecting the trunk from said one branch and for connecting it to the other branch.

9. In a, telephone system, a trunk connecting two exchanges, a normally connected branch and a normally disconnected branch for the trunk at one exchange, means for extending a call to the trunk at the other exchange, an operators link 5 and means for connecting it to said first branch to answer the call, and means controlled over the trunk line for disconnecting the trunk from said first branch and for connecting it to said second branch pending the disconnection of the link cir- 7 cuit from said first branc 10. In a telephone system, a trunk connecting two exchanges, a normally connected branch and a normally disconnected branch for the trunk at one exchange, a signal associated with each 75 branch, means for extending a call to the trunk each of said branches, means for extending a call at said other exchange, means responsive to the from said calling line over said trunk circuit and call for operating the signal associated with said one of said branches to one of said link circuits, first branch, a link circuit and means for com means controlled from said calling line for releasnecting it to said first branch to answer the call, ing said call, and means automatically responsive means for terminating said call and for extendto the release of said call for connecting said 5 ing a second call to the trunk at said other extrunk to the other of said branches so the next change, and means responsive to said second call call over the trunk will be extended over said for operating the signal associated with said secother link circuit. 0nd branch provided said link circuit is still con- 13. In a telephone system, a trunk, a jack nor- 10 nected to said first branch. mally terminating the talking conductors of said 11. In a. telephone system, a trunk circuit, two trunk, operator controlled means including a branches at one end of said trunk, a separate plug and cord circuit for establishing a. connecoperator's link circuit for each of said branches, tion over said trunk and jack between a calling means for extending a call over said trunk and and a called party, and means in said trunk con- 15 one of its branches to a link circuit, and means trolled by the calling party in response to hangresponsive to the terminaton of said call for coning up his receiver for opening the talking connecting the other branch of said trunk to said ductors of said trunk to break the talking conother link circuit. nection to said jack while said plug of the cord 12. In a, telephone system, a calling line, a circuit is maintained connected to said jack. 20 trunk circuit, separate branches in which said trunk terminates, an operator's link circuit for PHILLIP A. BOLANDER. 

